Manufacture of nitrogenic and phosphatic combinations



Patented Oct. I 27 1925.

UNITED STATES SBAIII'EN JOSEPH BRESLA ER, or GENEVA, SWITZERLAND, amGEORGES- GHERA, ITALY, ASSIGNORS 'ro socmm or oEnEvA, SWITZERLAND, aOORPOR T oi-"Pics. I

nE'rUbEs cnrmouns roux nmnns'ram, ATION or swnzaansnn.

MANUFACTURE OF NITROGENIO AND PHOSPHATE? COMBINATIONS.

Drawing, Original application filed September 18, 1920, Serial- 1T0.411,074. Divided and this application filed Kay 29, 1925. Serial No.88,835.-

To all whom it may concern: 4

Be it known that we, J OSEPH BRESLAUER, a citizen of Switzerland,residing at Geneva, Switzerland,"and GEORGES DARIER, a citizen ofSwitzerland, residing at Bordighera, in Italy, have invented certain newand useful Improvements in Manufacture of Nitrogenie and, PhosphaticCombinatmns, of which the following is a specificatwn.

Our present invention relates to a process I of producing fertilizersand, more particularly, to a process of transforming crude calciumcyanamid to substances which may be mixed with other fertilizingmaterials, such as phosphates, in the formation of a completefertilizer. The present application is a division-of our co-pendingapplication Serial No. 411,- 074, filed Sept. 18th, 1920. Calciumcyanamid or raw. cyanamid possesses physical characteristics whichrender its application as a fertilizer difficult and has an alkalinity,due to the presence of lime or loosely combined calcium, that causes itto react with acid phosphates with which it may be mixed, changing themto insoluble phosphates, and thus renders it difficult or impossible tocombine-the nitrogenic constitbe directly mixed with uents of the rawcyanamid with soluble or acid phosphates requisite in the formation of acomplete fertilizer. These obstacles are overcome in thejprocessdescribed in the above application, from which the present applicationis divided, by transforming the raw cyanamid into free cyanamid. andthence into urea or salts of urea which may fertilizing materials. Thepresent invention relates to modifications and improvemeits on theprocess of the above identified application and has among its objects tosi the process of forming the urea and the phosphate and nitrogeniccompositions; to produce fertilizers of somewhat different physicalproperties and chemical composition; to provide a process in which theurea may be isolated and the remaining mother liquors utilized in theformation of a nitrophosphates and other 'plify and cheapen' genie andphosphatic fertilizer; and to provide a process in which the acid usedin the production of the urea is again utilized in v the formation ofsoluble phosphates.

cyanamid in small portions to water and keeping it suspended therein bysuitable agitation while the water is continuously supplied with agaseous acid which forms insoluble compounds with the metallicconst-ituents or impurities of the raw cyanamid. During thisdecomposition of the cyanamid, the temperature of the water ismaintained sufficiently low to avoid or inhibit the polymerization ofthe free cyanamid to dicyan- 'diamid, a temperature below 40 C. beingpreferable for this purpose, particularly when a weak acid, such ascarbonic acid, is used and the acidity of the solution may become verylow. The solution of free cyanamid may be brought to any desired degreeDARIER, or nonmof concentration by removing the precipia temperatureoffrom 60 C. to

acid to the clarified'soluthe free acid of the solution combines andfrom which soluble hosphate constituents for a complete fertihzer areobtained. The.

mother liquors remaining from the crystallizing of the urea salts mayalso be used to convert calcium phosphate to soluble phosphate or may beadded to calcium phosphate to which the crude urea solution haspreparation of subsequent solutions of free been added therebyincreasing the quantity cyanamid by the addition of raw cyanamid" ofsoluble phosphate and-adding the nitroand carbon dioxide as describedabove. The genie compounds present in the mother precipitated calciumcarbonate may be utiliquor. lized for neutralizing acid solutions, forthe 7 In forming the solution of free cyanamid, production'of Portlandcement or for other i any suitable acid may be used to neutralizetechnical purposes.

and remove the calcium and other metallic The filtered or. clarifiedsolution of free constituents combined with the cyanacyanamidthusobtained is, acidified with mid or present as impurities, I but asulphuric acid and isthen heated to a tem- 75 gaseous acid capable offorming insoluperature of from C. to C. and mainble salts with thesemetals is preferred. For tained at'this temperature for about one halfexample sulphur dioxideor carbon dioxide hour to transform the freecyanamid into may be used, carbon dioxide being preferurea by reactionwith the water of the soluable as it is more readily available. Thetion, the acidvserving to catalyze this reacraw cyanamid is added in afinely divided tion and'also uniting with the urea thus condition insuccessive small portions ,and formed to form acid solution of urea. Asthe gaseous acid is supplied in quantities dicyandiamid is not formed inacid solution sufficient to precipitate the calcium and even at theseelevated temperatures, the free other metallic constituents of the rawcyanacyanamid may in this manner be changed mid and form a slightly acidsolution and to urea without danger of forming appreciis added at a raterelative to the addition of able quantities of dicyandiamid.

the raw cyanamid to maintain the solution The urea or acid solution ofurea thus as nearly acid as vpracticable. During the formed'contains thenitrogen of the cyana addition of the raw cyanamid, the solution mid ina form that may be used directly as is vigorously stirred or agitated inorder-to a nitrogenic fertilizer or may be mixed with maintain theparticles of raw cyanamid 1n phosphatic and potassium salts to form a afinely divided separated condition and suscomplete fertilizer. The ureamay be 150-- pended in the solution and thus bring the lated from thesolution by evaporating at a raw cyanamid into the most intimate conlowtemperature and crystalhzmg from the feet with the carbonic acidsolution. solution, leaving a mother liquor containing During theaddition of the raw cyanamid a quantity of free acids and nitrogenousmato the acidified water, excessiveheating of terials which may be addedto phosphatic the water should be avoided to avoid the materials orphosphatic and nitrogenous maolymerization of substantial quantities ofterials to increase their content of nitrogen. the free cyanamid in thesolution into dicy- Then it is desired to crystallize and isolateandiamid. As considerable heat is liberated the urea in this manner, buta small amount in the addition of the cyanamid and formaof the sulphuricacid is preferably used. tion of the calcium salts, the solution may QThe solution of urea may be combined (11- be cooled artificially whenthe dissipation rectly with phosphates in forming amlxed of heat isnot'sufliciently rapid during the fertilizer. As the solution containssome addition of the raw cyanamid. The temperafree acid and some acidweakly combine ture should not be permitted to rise above with the urea,it may serve for converting 40 C. and is preferably held approximatelyinsoluble calcium phosphates such as phosbetween 30 C. and 40 C. phaterock, bone powder, or basic slag, into During the addition of the rawcyanamid, soluble acid phosphates. By the addition of the insoluble orprecipitated metallic salts phosphate rock or other tricalcium phosinthe solution continuously increase, eventuphates, a fertilizer maybeformed having 'ally becomingygreat enough to interfere nitrogemc andphosphatic compounds preswith the stirring and circulation of the cut inany desired proportions, and, as the liquid. To obtain asolution of agreater acid used in converting free cyanamid to concentration of freecyanamid than is oburea is used primarily as catalyzer, it tained whenthis point is reached, the inmay be added in any desired quantity tosoluble salts of calcium and other metals are the solution of freecyanamid and the quanremovedfrom the solution by filtration or tity maybe selected to convert the desired equivalent methods and the additionof powquantity of phosphate rock in the later step dered or finelydivided raw cyanamid and of mixing the acidin'ea solution with thecarbon dioxide is continued or repeated, the phosphate rock; removal ofthe precipitated salts and 'fur- The acid solution of urea solublephosther addition of raw cyanamid being repeatphate, which also containscalcium sulphate, 12E

ed until a solution of the desired conce'ntrais then evaporated untilonly suflicient wation is obtained. The removed precipitates ter remainsto unite with the calcium sulare then washed with water to remove thephate to form crystals similar .to plaster of traces of free cyanamidadhering thereto Parisand to thus cause the mass to solidify. and thewash waters are utilized for the Other salts ha :ing fertilizing value.such 13' claim. and

as kainite (MgSOiz KCl) may be added to I the solution of urea, or saltsmay be added to unite with and take up the water of the' solution informing The mixture is filtered and the precipitate of insoluble salts,

washed free of cyanamid for use in a subsequent extraction.

To the filtered solution of free cyanamid there is added about 7 kgs. ofconcentrated sulphuric acid, and the solution is heated to 70 C. forhalf an hour. The cyanamid is thereby converted by hydration into ureaaccording to the equat1on:

CNQH, H2O 1 5:

'lricalcium quantity suflicient to be completely con verted into solublephosphate as, for example, in accordance with the following equation IThe resulting solution is evaporated under a vacuum. I

Through the above process, therefore, the raw cyanamid is converted intoa nitrogenic compound suitable for mixing with other fertilizingconstituents to form a mixed fertilizer without appreciable cost' isdesired that all matter contained in the above description shall beinterpreted as illustrative and not in a limiting sense.

Having described our invention, what we desire to secure by LettersPatent is: 4

1. A process of the type described which comprises, introducing rawcalcium cyanphosphate is then added in' I mately 60 C; to 70 amid insmall portions in a finely divided condition into water maintained atjatem-' perature between approximately C. and 40 C., to which is added anacid forming insoluble salts'with the metallic impurities of said rawcalcium cyanamid to, precipitate the impurities of each portion asadded,

removing the precipitated insoluble salts and converting the resultingfree cyanamid in solution to urea by sulphuric acid.

2. A process of the type describedwhich comprises, introducing ,rawcalcium cyanamid in small portions in a finely divided condition intowater acidified with carbon dioxide and vigorously agitated, andconverting the resulting free cyanamid in solution to urea by the actionof sulphuric ,acid.

3. A process of the type described which comprises, introducing rawcalcium cyan-- amid in small portions in a finely divided condition intowater acidified forming insoluble salts with the metallic impurities ofsaid raw calcium cyanamid, and converting the resulting free cyanamid insolution tourea by sulphuric acid.

4. A comprises, adding finely divided raw calcium cyanamid in successivesmall portions to water acidified with an acid forming insolublecompounds with metallic constitucuts of said raw calcium cyanamid,agitating said water during said addition, removing the insoluble saltsthus formed, then acidifying said solution with sulphuric acid andheating it to a temperature of approxi- C. to transform the freecyanamid in solution to urea.

5. A process of the type described which comprises, adding finelydivided -ra\v calcium cyanamid in successive small portions to waterwhile acidified with carbonic acid to form a solution offree cyanamid,agitat ing said solution while adding said raw cal cium cyanamid,removing theinsoluble salts thus formed, then-acidifying-said solutionwith sulphuric acid and heating it to a temperature of approximately C.to C. to transform the free cyanamid in solution to urea. v

6. A process of the type described which comprises, adding finelydivided raw calcium cyanamid in successive small portions to Water,agitating said water during the addition of said raw calcium cyanamid,maintaining carbonic acid in said solution to precipitate the metallicconstituents of said raw calcium cyanamid and slightly acidity saidsolution, while maintaining said solution at a relatively lowtemperature to avoid polymerization of the free cyanamid thus formed.removing the insoluble-salts from the solution. acidifying the solutionwith sulphuric acid and heating it to ap-' proximately 60 C. to 70 C. toform urea.

with an acid process of the type described which to 70 C. to

'to water into which there is directed a current of carbon dioxide toprecipitate the metallic constituents of said raw calcium cyanamid andslightly acidity the solution, removing the precipitate. acidifying thesolution with sulphuric approximately 60 C. to 70 C. to form urea.

8. A process of the type described which. comprises, adding finelydivided raw calcium cyanamid in successive small portions to water whiledissolving therein carbon dioxide to precipitate the metallicconstituents of said raw calcium cyanamid and slightly acidity thesolution and constantly agitating said solution during said addition,removing the precipitated salts and repeat-- ing the addition of acidand raw calcium cyanamid, said solution being at a relatively lowtemperature, acidifying the resulting solution with sulphuric acid andheating it to a temperature of approximately 60 C. to 70 C. to hydratethe free cyanamid to urea.

9. A process of the type described which comprises, adding finelydivided raw calcium cyanamid in successive small portions 'to watermaintained at a sufficiently low temperature to prevent substantialpolymerization of free cyanamid while supplying carbon dioxide inquantity suiiicient to precipitate the metallic constituents of said rawcyanamid and to form a slightly acid solution, removing the precipitatedcompounds and repeating the addition of raw calcium cyanamid to saidsolution, acidifying the resulting solution with sulphuric acid andheating it to a temperature of from 60 C. hydrate the free cyanamid tourea.

10. A process of the type described which comprises, adding finelydivided raw calcium cyanamid in successive small portions to water whileagitated andacidified with carbonic acid, while maintaining saidsolution at a relative low temperature of ap-- C. to avoid theproximately C. to

of the free cyanamid in sopolymerization lution, removing the insolublesalts thus formed and. repeating the addition of acid andraw calciumcyanamid to form a concentrated solution of free cyanamid, acidifyingsaid solution with sulphuric acid and heating it to a temperature offrom (J. to? 0 C. to hydrolyze said free cyanamid to urea.

11. A process of the type described which comprises, adding finelydividedraw calium cyanamid in successive small portions solution withcarbondioxide at a rate to precipitate the .metallic constituents ofsaid raw calcium form a slightly acid anamid substantially as added andto solution, said solution being agitated during the addition of the rawcalcium cyanamid and maintained at a temperature of approximatelybetween 30 C. and 40 C. to avoid polymerization of the free cyanamid ofthe solution, acidifying the resulting solution of free cyanamid withsulphuric acid and heating it to a temper-ature of approximately 60 C.to C.

acid and heating it to hydrolyze the free cyanamid in solution to urea.

' 12./A process of thectype described which comprises, adding finelydivided raw calcium cyanamid in successive small portions to wateracidified witi. carbonic acid to form a solution of free cyanamid. saidsolution being agitated during said addition, removing the insolublesalts thus formed, acidifying the resulting solution with sulphuricacid. heating the acidified solution to approximately 60 C. to 70 C. tohydrolyze the fre-e cyananiid in solution to urea, crystallizing theurea from said solution and adding the resulting mother liquors-to aphosphate. 1

- 1?). A processot the type describedwhich comprises, introducing rawcalcium cyanamid in small portions in a finely divided condition into anacid solution, heating the resulting free cyanamid in solution acidifiedwith sulphuric acid to form urea, and treating an insoluble phosphatewith the resulting acid solution of urea to form a mixed nitrogenic andphosphate fertilizer. 14. A process of the type described which,comprises, introducing raw calcium cyanamid in small portions in afinely divided condition into water acidified with carbon dioxide whileagitating said solution, re

' moving the insoluble salts thus formed,

acidifying the resulting solution with sulphuric acid to h drolyze thefree cyanamid to urea and adding the resulting acid solution of urea toan insoluble convert the phosphate to a soluble phate.

15. A process of the type described which compisises, introducing rawcalcium cyanamld in small portions in a finely divided condition intowater acidified with carbon dioxide while agitating said solutionremoving the insoluble salts thus formed, acidifying the resultingsolution with sulphuric acid to hydrolyze the free cyanamid to urea andadding the resulting acid solution of urea totricalcium orthophosphateto convert the phosphate to a soluble phosphate. J s i 16. A processaccording to claim 15 in which a natural phosphate is used as theinsoluble phosphate. I 1 17. A process according to claim 15 in whichbone powder is used as the insoluble phosphate. 4

' 18. A process of comprises, adding phosthe type described which finelydivided raw calphosphate to. 1

cium cyanamid in successive small portions to water acidified withcarbonic acid to form a solution of free cyanamid, the solution beingagitated during said addition,

removing the insoluble salts thus formed,

acidifying the resulting solution of free cyanamid with sulphuric acidand heating it to approximately 60 C. to 70 C. to hydrolyze the freecyanamid to urea and treat cium cyanamid in successive small ortions towater acidified with carbonic acid while continuously a itating themixture, removin the insolu le salts, acidifying the resu ting solutionof free cyanamid with sulphuric acid and heating it to a temperature of60 C. to 70 C. to transform the free cyanamid in solution to urea,treating calcium phosphate with the resulting acid mixture, andevaporating the resulting solution until it forms a solid mass throughthe crystallization of the calcium sulphate formed in the solution.

20. A process of the type described which comprises, adding finelydivided raw calcium cyanamid in successive small portions to wateracidified with carbonic acid,while agitating the mixture,'removing theinsolu ble salts thus formed and adding additional quantities of rawcalcium cyanamid to form a concentrated solution, acldifying saidsolution with sulphuric acid andheatin it to a temperature of from 60 C.to 70 to transform the free cyanamid in solution to solution, saidheating the acidified solution urea, treating calcium phosphate with theresulting acidmixture, and evaporating said solution to form a solidfertilizer.

21. A process of the type described which comprises, adding finelydivided. raw cal-' cium cyanamid in successive small portions towateracidified with carbonic ac1d,while agitating the mixture, removing theinsoluble salts from the solution, acidifying the solution withsulphuric acid, heating the solution to a temperature of from 60 C. to70 C. to form a solution of urea, crystallizing urea from-said solution,and adding the mother liquors and an acid solution 01 urea to calciumphosphate.

22. A process of the type described which comprises, adding finelydivided raw calcium cyanamid in successive small portions to water towhich carbon dioxide is supplied in quantity to form insoluble saltswith the metallic im urities of the raw calcium cyanamid and slightlyacidify the-resulting solution being at a sufficiently low temperatureto prevent substantial change in the free cyanamid formed therein,adding sulphuric acid to to 'a temperature of approximately 60 C. to C.and adding the resulting acid solution or .urea to an insolublephosphate.

23. A process according to claim'21 in whichdbut a small quantity ofsulphuric acid is use said solution,

In testimony whereof, we affix our signatures.

JOSEPH BRESLAUER. GEORGES DARIER.

